ARTICLE pubs.acs.org/JAFC
Vapor-Phase Toxicity of Derris scandens Benth.-Derived Constituents against Four Stored-Product Pests Atmakur Hymavathi,† Peta Devanand,‡ Katragadda Suresh Babu,† Thonthula Sreelatha,† Usha Rani Pathipati,‡ and Janaswamy Madhusudana Rao*,† †
Division of Organic Chemistry-I, Natural Product Laboratory, Indian Institute of Chemical Technology (CSIR), Tarnaka, Hyderabad 500 607, India ‡ Biology and Biotechnology Division, Indian Institute of Chemical Technology (CSIR), Tarnaka, Hyderabad 500 607, India ABSTRACT: The vapor-phase toxicity of Derris scandens Benth.-derived constituents was evaluated against four stored-product pests (Callosobruchus chinensis L., Sitophilus oryzae L., Rhyzopertha dominica L., and Tribolium castaneum H.) using fumigation bioassays and compared to those of commonly used insecticides. The structures of all constituents of were characterized by spectroscopic analyses [nuclear magnetic resonance (NMR) and mass spectrometry]. The sensitivity of the test insect to compounds varied with exposure time, concentration, and insect species. Over 100% mortality after 24 h was achieved with the compounds osajin (2), scandinone (5), sphaerobioside (8), and genistein (9) against all of the test insects, while laxifolin (3) and lupalbigenin (4) showed 100% mortality after 72 h against T. csataneum and R. dominica. Scandenone (1), scandenin A (6), and scandenin (7) were less effective. Among the insects, C. chinensis, S. oryzae, and R. dominica were more susceptible to the treatments, whereas T. castaneum was less susceptible. The results of fumigation tests indicated that compounds from D. scandens whole plant extract are potential candidates to control stored-product pests. KEYWORDS: Derris scandens, insecticidal activity, stored pests, Callosobruchus chinensis, Sitophilus oryzae, Rhyzopertha dominica, Tribolium castaneum, vapor-phase toxicity
’ INTRODUCTION The adzuki bean weevil, Callosobruchus chinensis L. (Coleoptera: Bruchidae), rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), lesser grain borer, Rhyzopertha dominica F. (Coleoptera: Bostrichidae), and red flour beetle, Tribolium castaneum H. (Coleoptera: Tenebrionidae) are the most widespread and destructive insect pests of stored grains as well as stored products.1-5 Globally, about 10-30% of produced grains are lost every year due to insect damage.6 Control of these pests is primarily dependent upon repeated application of synthetic insecticides.7 The continuous use of synthetic insecticides for the eradication of insects has been effective but, nevertheless, has led to the development of pest resistance through the disruption of biological systems.8,9 Plants may provide potential alternatives to currently used insectcontrol agents because they constitute a rich source of bioactive chemicals, are often active against a limited number of species, including specific target insects, are biodegradable to nontoxic products, and are potentially suitable for use in integrated pest management (IPM) programs. As a part of our ongoing search for natural agrochemicals from Indian medicinal plants, we have thus far investigated the potential of species in the Fabaceae family. Derris scandens (Fabaceae), known by its common name gonj (Hindi), is widely distributed throughout India.10 One of the potential applications of the Derris species is the use to the control phytophagous pests. D. scandens root is an excellent insecticide, being harmful to chewing and sucking insects but not human beings. In a previous work, we reported the isolation of a new benzyl derivative along with several insecticidal constituents from D. scandens, which is r 2011 American Chemical Society
one of the dominant species of the south Indian forest.11 These results have encouraged us to undertake the further studies of insecticidal activity against various stored-product insect species. Now, following the study of this plant, we have tested the isolates against the stored pest insects for their insecticidal activity. Herein, we report the insecticidal activity of isolates (1-9) from D. scandens against four major stored-product pest insect species viz. C. chinensis L. (Coleoptera: Bruchidae), S. oryzae L. (Coleoptera: Curculionidae), R. dominica F. (Coleoptera: Bostrichidae), and T. castaneum H. (Coleoptera: Tenebrionidae).
’ MATERIALS AND METHODS General Procedures. All solvents were distilled before use and were removed by rotary evaporation at temperatures up to 40 °C. 1H and 13C nuclear magnetic resonance (NMR) spectra were measured on a Bruker 300 MHz spectrometer using tetramethylsilane as an internal standard. Mass spectra were recorded on VG Auto Spec-M [fast atom bombardment mass spectrometry (FABMS)], and the infrared spectra were recorded on a Thermo Nicolet Nexus 670 Fourier transform infrared (FTIR) spectrometer. Melting points were measured on a Fischer Scientific melting point apparatus and are uncorrected. Column chromatography was carried out using 60-120 mesh silica gel (Merck). Thin-layer chromatography (TLC) was performed using precoated silica gel 60 F254 TLC plates, visualized with a UV lamp, and then dipped in 5% H2SO4 solution followed by Received: August 31, 2010 Accepted: January 21, 2011 Revised: January 18, 2011 Published: February 11, 2011 1653
dx.doi.org/10.1021/jf104411h | J. Agric. Food Chem. 2011, 59, 1653–1657
Journal of Agricultural and Food Chemistry
ARTICLE
Figure 1. Compounds isolated from D. scandens Benth. heating. The optical rotations were measured on a Jasco Dip 360 digital polarimeter. Test Insects. Test insects were obtained from laboratory cultures of the Entomology Division, Directorate of Maize Research, RajendraNagar, Hyderabad, India. Green gram (Phaseolus mungo L.) (Fabaceae) for C. chinensis and wheat (Triticum aestivum L.) for S. orazae, R. dominica, and T. castaneum are the respective rearing medium for test insects. Insect rearing was maintained in the laboratory of the Indian Institute of Chemical Technology (IICT), Hyderabad, India. The cultures were maintained at 28 ( 2 °C and 65 ( 5% relative humidity. Plant Material. The whole plant of D. scandens was collected from the Tirumala Forest, Tirupati, Andhra Pradesh, India, in August 2005. It was authenticated by Dr. K. Madhava Chetty, Department of Botany, Sri Venkateswara University, Tirupati, India. A voucher specimen was deposited in the herbarium of the Botany Department, Sri Venkateswara University, Tirupati, India. Extraction and Isolation of the Compounds. The whole plant of D. scandens (5 kg) was shade-dried, powdered, and extracted with chloroform in a Soxhlet apparatus for 72 h at 50 °C. The resulting chloroform extract was evaporated to dryness under reduced pressure, affording a syrupy residue (21 g). Then, this chloroform extract was subjected to column chromatography on a silica gel column (60-120 mesh, 150 15 cm) and eluted with a stepwise gradient of hexane/ EtOAc (98:2, 95:5, 92:8, 90:10, and 88:12 by volume) to give seven fractions (F1, F2, F3, F4, F5, F6, and F7). Fraction F2 was chromatographed on silica gel (60-120 mesh) column using hexane/EtOAc (99:1 and 98:2, by volume) to give compound 1 (0.2 g) and compound 2 (0.08 g). Fraction F4 was concentrated under reduced pressure to give compound 3 as a pale yellow solid (0.12 g). Fraction F5 was extracted with hexane to obtain compound 5 (5.8 g) as a residue. The filtrate was concentrated to give compound 4 (4.6 g) as a pale yellow solid. Fraction
F6 was concentrated to give a dark brown residue (2.5 g), which was chromatographed on a 100-200 mesh silica gel column with an isocratic elution of the solvent system of hexane/chloroform/acetone (80:15:5, by volume) to give two subfractions A and B, which were further fractionated on a silica gel column with isocratic elution of chloroform/ carbon tetrachloride/acetone (55:40:5, by volume) to give compound 6 (0.26 g) and compound 7 (1.2 g). Fraction F7 was chromatographed on a silica gel column (60-120 mesh, 50 5 cm) and eluted with a stepwise gradient of chloroform/methanol (90:10 and 85:15, by volume) to give compounds 8 (2.8 g) and 9 (3.9 g). All of these compounds were identified as scandenone (1),12 osajin (2),12 laxifolin (3),13 lupalbigenin (4),14 scandinone (5),14 scandenin A (6),14 scandenin (7),14 sphaerobioside (8),15 and genistein (9),16 from 1 H and 13C NMR data comparison to those reported in the literature (Figure 1). Bioassay. The insecticidal properties of isolated compounds from D. scandens were evaluated against adults of four stored-product insects by the fumigation assay.17 In this method, 20 adults of 3-8-day-old C. chinensis, S. oryzae, R. dominica, and T. castaneum were separately placed on the bottom of a polyvinyl chloride (PVC) container (100 mL) and then covered with a lid. Appropriate concentrations (0.1-1.0 μg/mL) of each tested material in acetone were applied to filter papers (Whatman No. 1; 2 3 cm diameter). After drying in a fume hood for 5 min, each treated paper was attached to the inner side of a lid with a small amount of solid glue and the container was covered with the lid. Control filter papers received 50 μL of acetone. The tests were carried out at 28 ( 2 °C temperature and 65 ( 5% relative humidity. Mortality was ensured by probing the insect body with a slender paintbrush. Dead insects were counted every 24 h for a total period of 72 h post-treatment. There were five replicates per treatment, and the tests were repeated 3 times on different dates each time, to avoid any day-to-day variation. 1654
dx.doi.org/10.1021/jf104411h |J. Agric. Food Chem. 2011, 59, 1653–1657
Journal of Agricultural and Food Chemistry
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Table 1. Insecticidal Activity of Isolated Compounds from D. scandens against C. chinensis by the Fumigation Method toxicity (%)a (1.0 μg/mL) LC50(95% CL)b (μg/mL)
compounds
24 h
48 h
72 h
1
27.9 ( 5.1 c
29.1 ( 3.6 e
31.4 ( 2.8 f
2
100 ( 0.0 b
3
88.8 ( 6.8 a
93.2 ( 3.4 d
>1.0
96.4 ( 3.7 d
χ2 (df)
p level
1.78 (5)
0.774
0.29 (0.06-0.38)
35.05 (5)
0
0.39 (0.26-0.55)
14.62 (5)
0.005
4
100 ( 0.0 b
0.23 (0.10-0.36)
23.08 (5)
0.001
5
100 ( 0.0 b
0.31 (0.14-0.53)
34.43 (5)
0
6
79.0 ( 5.7 e
81.4 ( 2.5 a
83.0 ( 4.1 a
0.43 (0.39-0.47)
3.38 (5)
0.495
7
49.5 ( 6.6 d
56.0 ( 2.8 c
58.2 ( 3.3 e
0.90 (0.81-1.02)
3.12 (5)
0.528
8 9
100 ( 0.0 b 100 ( 0.0 b
0.21 (0.16-0.35) 0.17 (0.12-1.00)
23.93 (5) 126.6 (5)
0.001 0
a Values are the mean ( standard deviation (SD). Each column followed by the same letter is not significantly different from another (one-way ANOVA; Tukey test at 1.0
5.37 (5)
0.32 (0.11-0.57)
5
100 ( 0.0 ca
6
60.6 ( 4.0 e
64.2 ( 3.9 a
67.8 ( 5.4 g
7
72.3 ( 6.5 f
75.8 ( 2.7 b
78.2 ( 3.0 b
8 9
100 ( 0.0 c 100 ( 0.0 c
44.41 (5)
0.74 (0.61-0.94)
5.84 (5)
0.27 (0.11-0.45) 0.28 (0.08-0.51)
27.4 (5) 50.49 (5)
0.250 0
0.210 0 0
Values are the mean ( SD. Each column followed by the same letter is not significantly different from another (one-way ANOVA; Tukey test at 1.0
χ2 (df) 122.4 (5)
0.26 (0.13-0.41)
27.29 (5)
p level 0 0
3
92.3 ( 5.4 a
94.6 ( 1.3 a
100 ( 0.0 a
0.34 (0.27-0.40)
4.05 (5)
0.398
4 5
85.4 ( 3.9 d 100 ( 0.0 e
88.4 ( 3.1 c
91.0 ( 2.6 d
0.38 (0.32-0.45) 0.20 (0.16-0.28)
4.71 (5) 10.42 (5)
0.318 0.033
6
58.2 ( 6.1 c
60.8 ( 3.2 d
63.8 ( 4.6 e
7
24.7 ( 1.0 b
29.6 ( 1.9 b
32.2 ( 1.7 c
0.82 (0.74-0.94) >1.0
1.23 (5)
0.993
11.98 (5)
0.017
8
100 ( 0.0 e
0.20 (0.08-0.31)
17.68 (5)
0.001
9
100 ( 0.0 e
0.18 (0.10-0.26)
9.95 (5)
0.041
Values are the mean ( SD. Each column followed by the same letter is not significantly different from another (one-way ANOVA; Tukey test at
